Method of manufacturing semiconductor device

Abstract

An object of the invention is to provide a semiconductor device having improved performance. A method of manufacturing a semiconductor device includes: forming a trench and then forming a first insulating film made of a silicon oxide film through CVD using a gas containing an O 3 gas and a TEOS gas to cover the side surface of the trench with the insulating film; forming a second insulating film made of a silicon oxide film through PECVD to cover the side surface of the trench with the second insulating film via the first insulating film; and forming a third insulating film made of a silicon oxide film through CVD using a gas containing an O 3 gas and a TEOS gas to close the trench with the third insulating film while leaving a space in the trench.

What is claimed is: 
     
       1. A method of manufacturing a semiconductor device, comprising:
 (a) forming a trench portion in a main surface of a semiconductor substrate; 
 (b) forming a first insulating film having a silicon oxide film in the trench portion and over the main surface of the semiconductor substrate by chemical vapor deposition; 
 (c) forming a second insulating film having a silicon oxide film over the first insulating film by plasma chemical vapor deposition; and 
 (d) forming a third insulating film having a silicon oxide film over the second insulating film by chemical vapor deposition, 
 wherein in (b), the first insulating film covers a first side surface of the trench portion, 
 wherein in (c), the second insulating film covers the first side surface of the trench portion via the first insulating film, 
 wherein in (d), the third insulating film closes therewith the trench portion while leaving a space in the trench portion, and 
 wherein a step coverage property of the second insulating film is lower than those of the first insulating film and third insulating film. 
 
     
     
       2. The method of manufacturing a semiconductor device according to  claim 1 , further comprising:
 (e) forming a fourth insulating film having a silicon oxide film over the third insulating film by plasma chemical vapor deposition. 
 
     
     
       3. The method of manufacturing a semiconductor device according to  claim 1 , further comprising:
 (f) forming a fifth insulating film over the main surface of the semiconductor substrate; and 
 (g) forming an opening portion penetrating through the fifth insulating film and reaching the semiconductor substrate, 
 wherein in (a), the trench portion to communicate with the opening portion is formed by etching the semiconductor substrate exposed from the opening portion, 
 wherein in (b), the first insulating film covers a second side surface of the opening portion, 
 wherein in (c), the second insulating film covers the second side surface of the opening portion via the first insulating film, and 
 wherein the method of manufacturing the semiconductor device further comprises: 
 (h) after (a) but prior to (b), retreating the second side surface of the opening portion from the first side surface of the trench portion. 
 
     
     
       4. The method of manufacturing a semiconductor device according to  claim 3 , further comprising:
 (i) forming a sixth insulating film having a silicon nitride film over the fifth insulating film, 
 wherein in (f), the fifth insulating film has a silicon oxide film, and 
 wherein in (g), the opening portion is formed to penetrate the sixth insulating film and the fifth insulating film and to reach the semiconductor substrate. 
 
     
     
       5. The method of manufacturing a semiconductor device according to  claim 4 , further comprising:
 (j) forming a seventh insulating film having a silicon oxide film over the sixth insulating film, 
 wherein in (g), the opening portion is formed to penetrate through the seventh insulating film, the sixth insulating film, and the fifth insulating film and to reach the semiconductor substrate, and 
 wherein (h) comprises:
 (h1) etching a portion of the sixth insulating film exposed from the second side surface of the opening portion to retreat the sixth insulating film from the first side surface of the trench portion; and 
 (h2) after (h1), the seventh insulating film is removed by etching and a portion of the fifth insulating film exposed from the second side surface of the opening portion is etched to retreat the fifth insulating film from the first side surface of the trench portion. 
 
 
     
     
       6. The method of manufacturing a semiconductor device according to  claim 4 , further comprising:
 (k) forming an eighth insulating film having a silicon oxide film over the sixth insulating film, 
 wherein in (g), the opening portion is formed to penetrate through the eighth insulating film, the sixth insulating film, and the fifth insulating film and to reach the semiconductor substrate, and 
 wherein (h) comprises:
 (h3) etching the eighth insulating film to retreat the insulating film from the first side surface of the trench portion, and etching a portion of the fifth insulating film exposed from the second side surface of the opening portion to retreat the fifth insulating film from the first side surface of the trench portion; and 
 (h4) after (h3), etching the sixth insulating film to retreat the insulating film from the first side surface of the trench portion. 
 
 
     
     
       7. The method of manufacturing a semiconductor device according to  claim 3 , comprising:
 (l) forming a ninth insulating film having a silicon nitride film over the fifth insulating film; and 
 (m) forming a tenth insulating film having a silicon oxide film over the ninth insulating film, 
 wherein in (f), the fifth insulating film has a silicon oxide film, 
 wherein in (g), the opening portion is formed to penetrate through the tenth insulating film, the ninth insulating film, and the fifth insulating film and to reach the semiconductor substrate, 
 wherein in (h), the tenth insulating film is removed by etching, and a portion of the fifth insulating film exposed from the second side surface of the opening portion is etched to retreat the fifth insulating film from the first side surface of the trench portion, 
 wherein the method of manufacturing a semiconductor device further comprises: 
 (n) after (c) but prior to (d), etching the second insulating film covering the second side surface of the opening portion with plasma. 
 
     
     
       8. The method of manufacturing a semiconductor device according to  claim 1 ,
 wherein in (c), the second insulating film is formed so as not to close the trench portion therewith. 
 
     
     
       9. The method of manufacturing a semiconductor device according to  claim 1 ,
 wherein in (c), the second insulating film is formed by plasma chemical vapor deposition using a gas containing a tetraethoxysilane gas. 
 
     
     
       10. The method of manufacturing a semiconductor device according to  claim 1 ,
 wherein in (c), the second insulating film is formed by plasma chemical vapor deposition using a gas containing a silane gas. 
 
     
     
       11. The method of manufacturing a semiconductor device according to  claim 2 ,
 wherein in (e), the fourth insulating film is formed by plasma chemical vapor deposition using a gas containing a tetraethoxysilane gas. 
 
     
     
       12. The method of manufacturing a semiconductor device according to  claim 2 ,
 wherein in (e), the fourth insulating film is formed by plasma chemical vapor deposition using a gas containing a silane gas. 
 
     
     
       13. The method of manufacturing a semiconductor device according to  claim 1 , comprising:
 (o) prior to (a), forming a semiconductor element over the main surface of the semiconductor substrate, 
 wherein in (b), the first insulating film covers the semiconductor element. 
 
     
     
       14. The method of manufacturing a semiconductor device according to  claim 13 ,
 wherein in (a), the trench portion surrounds the semiconductor element in plan view. 
 
     
     
       15. The method of manufacturing a semiconductor device according to  claim 13 ,
 wherein the semiconductor element is an LDMOSFET.